Sealed connection for heating elements and method of assembling



INVHVTOR. u A Josephine BY a a a wmwz fm Sept. 22, 1964 a. A. JOSEPHINESEALED CONNECTION FOR HEATING ELEMENTS AND METHOD OF ASSEMBLING FiledApril 14, 1960 United States Patent 3,150,344 SEALED CONNECTION FORHEATING ELEMENTS AND METHOD OF ASSEMELING Guy A. Josephine, Albion,Mich, assignor to McGraw- Edison Company, Milwaukee, Win, a corporationof Delaware Filed Apr. 14, 196i Ser. No. 22,261 7 Claims. (Cl. 338-329)This invention relates to a hermetically sealed con nection for a housedheating element and to the method of assembling the connection and isparticularly directed to a terminal connection made within an opening ina housing for a heating element through which the power supply lines areconnected to the heating element.

Electric heating elements of the immersion type are in serted freelyinto contained liquids. At times the heating unit is thrust into theliquid beyond the power supply connection and it is important that theconnection be hermetically sealed to prevent any leakage of electricityor power into the liquid in such an instance.

Immersion type heating elements are also employed to heat air which isvery humid. A hermetic seal is then also necessary to prevent similarpower loss.

Housed resistor electric heaters have been developed with the resistorheating element disposed within a metallic housing or sheath andembedded in a suitable electrically insulating and. heat conductingrefractory material to prevent shorting of the element. The refractoryembedding material must be thoroughly dry and protected against anymoisture in order to maintain and preserve the insulating and heatconducting characteristics of the refractory material which isconventionally employed. The housing is conventionally tubular shapedhaving one end open through which the heating element is interconnectedto incoming power lines. The open end is then hermetically sealed toprevent liquid leakage through the opening and thereby prevent passageof electricity to the immersing liquid or contaminating of therefractory material.

Various rigid and compressed sealing members have been employed to closethe opening about the power lead or supply line connections. Thus,vitreous material and similar rigid members have been disposed withinthe opening in attempts to seal the opening. Compressed rubber-likemembers have also been employed to establish a tight hermetic sealadjacent the opening. A particularly satisfactory sealed housingconstruction is disclosed in US. Patent No. 2,840,676 which issued June24, 1958, wherein a suitable fiowable material such as an epoxy resin isdisposed immediately adjacent the inner surface of an outer cover or capwhich is secured to the open end of the sheath or housing for theelement to seal the end of the housing. The terminal means of theheating elements projects outwardly through the sealing material and thecover to establish connection to incoming power lines.

The present invention is directed to a particularly inexpensiveconstruction for sealing the opening and completely encasing theconnection and to the method of as sembling the sealing members. Theconstruction and method of the present invention are more particularlyadapted to economical production of a commercial heater having apermanently sealed connection which is completely embedded within asuitable resilient fiowable material.

Generally, the present invention includes a sheathed heating elementhaving an opening through which a wirelike terminal connection is made.An insulating plug is supported within the sheathed housing and projectspartly into the housing terminating in spaced relation to the re-Patented Sept. 22, 1964 fractory embedding material. The insulating plugincludes a plurality of openings to accommodate the power supply linesand to allow introduction of a sealant through the plug and into thesheath and the openings in the plug after assembly of the plug over thesheath opening. Thus, with a conventional dual-conductor power line, apair of openings is provided one for each of the incoming power lines. Athird opening is provided through which the sealant is inserted into thesheath. The sealant flows into the cavity adjacent the sheath openingand then fiows backwardly and outwardly through the power leadconnection openings to completely fill the cavity in the housing and theopenings in the plug.

Although the third opening may beeliminated and the sealant poureddirectly through the lead-in openings, the third pouring openingsprovide a very rapid and inexpensive method of introducing the sealantinto the assembly to positively fill all voids. Consequently, thisprovides a very economical and practical construction or method ofassembling.

The sealant serves to hermetically close the lead-in opening and furtherbonds to the connection of the power supply lines and the terminal meansof the heating element to physically support the electrical connection.

The initial assembly is made by assembling the plug onto the power lineswith power lines projecting outwardiy from the plug. Connection of theterminal means and the incoming power lines is completed. After theconnection is made, the plug is slipped down over the connection andinto the lead-in opening with the inner end projecting partly into thehousing. The sealant material is then inserted through the specialfilling opening to completely fill the cavity and hermetically seal theopening upon setting of the material. The use of the plug reduces thequantity of the sealant which must be employed. This is importantbecause the sealant is normally the more expensive product employed inthe sealing of the opening. This sealant provides the necessary hermeticseal and insulation at the lead-in opening as well as physicallysupporting the electrical connection of the power supply line to theterminal means.

The present invention provides a very simple and rapidly assembledsealed terminal for electric immersion heaters and the like.

The drawing furnished herewith illustrates the best mode presentlycontemplated for carrying out the invention.

In the drawing:

FIG. 1 is a perspective elevational view of an immersion type heaterconstructed in accordance with the pres ent invention;

FIG. 2 is an enlarged vertical .section through the heater shown in FIG.1 illustrating the terminal connections in accordance with the presentinvention;

FIG. 3 is a vertical section through the heater of FIG. 1 taken on aplane at to the Vertical section of FIG, 2; and

FIG. 4 is a view of the heater 1 during the process of assembly of theillustrated embodiment of the invention.

Referring to the drawing and par ticularlyto FIGS. 1 and 2, an electricheater of the immersion variety is shown generally including a heatingunit 1 which is shown as a finned assembly for purposes of illustrationonly. The heating unit 1 is connected to a pair of power leads 2 by asealed terminal connection 3 which is constructed in accordance with thepresent invention.

The heating unit 1 includes an outertubular sheath 4 of a suitablematerial. Aluminum and the like are very satisfactory. One end of thesheath 4 is closed by an integral end wall 5 while the opposite end ofthe sheath 4 is opened to receive a generally U-shaped heating elecore7.

The heating element & is shown in outline only. In

actual practice, the element will normally take the shape of a doublespiral coil which extends axially through spaced openings in core 7.

The core 7 terminates within the sheath 4 and carries a'pair of embededterminal pins 8 connected to the adjacent ends of the U-shaped heatingelement 6. The pins 8 project axially outwardly from the core 7 andthrough the open end of sheath 4 for connection to power leads 2.

A suitable electrical insulating refractory material 9 such as magnesiumoxide or the like completely fills the space between the sheath 4, theceramic core 7 and the core openings accommodating the heating element 6in accordance with known construction. Material 9 alsocovers the end ofthe core 7 adjacent the pins ii for a predetermined depth substantiallyless than the depth of the cavity or chamber between the end of the core7 and the outer edge of the sheath 4.

A spiral fin 10 is integrally formed with the sheath 4 in theillustrated embodiment to increase the heat dissipating area of theheating unit 1, although the fin may be eliminated within the presentinvention. A separate end fin 11 is secured to the outer end of thesheath 4 as by welding or the like. The end fin 11 constitutes a nameplate and carries various indicia 12 including the recommended voltageof the incoming power leads 2, the Wattage of the unit, the manufacturerand the like.

The leads 2, constituting the power supply lines, are similar inconstruction and in connection to the pair of terminal pins 8 andconsequently only a single description is here given. Correspondingnumbers in the two connections identify corresponding elements.

The lead 2 is a standard commercial product consist ing of a strandedcable 13 which is enclosed within a suitable insulating cover 14 offlexible rubber or synthetic material such as neoprene. The end of thecover 14 is stripped back behind the end of the stranded cable 13 as at15 t-oreceivea connector clip 16 which is adapted to interconnect theincoming end of the lead 2 to a corresponding terminal pin 8-; generallyexteriorly of the outer end of the sheath 4 in the illustratedembodiment of the invention.

The connector clip 16 is generally of a standard type construction andincludes an outer split band 17 which is physically clamped about thestripped end 15 of the lead 2., An intermediate split band 18accommodates the. outer end. of a terminal pin 8 and the stripped end15. The split band 18 is clamped about the corresponding end of pin 8and stranded cable 13. Solder or the like 19 may be employed. at splitband 18 to insure good electrical connection of the pin 8' to thestranded cable 13. The connector clip 16 also includes an inner splitband 20 which is clamped about the outer end 21 of terminal pin Ktophysically interconnect and support the connection of the pin 8 to theconnector clip 16.

A tubular plug 22 encloses the connector clip 16 and the adjacent endsof lead 2 and pin 8.

The plug 22 is formed of a suitable insulating material and.ispreferably formed of nylon or the like. Plug 22 is generally acylindrical member having an outer diameter generally corresponding tothe diameter of the lead-in opening in the sheath 4. An intermediateflange 23-is integrally formed on the plug 22 and is adapted to seatupon the adjacent end fin 11 to properly locate the plug 22 with theinnermost end of the plug extending into the sheath 4: and terminatingin spaced relation to the refractory material 9; The inner end of theplug 22 is tapered as at 24 and the sheath 4 is correspondinglytaperedfor'a portion of the length of the inner end of tubular plug 22to establish a slight annular void 25 between the innermost end of theplug 22 and the adjacent surface of the sheathl. The-plug 22 includes apair of d lead-in openings 26 having a diameter slightly greater thanthe outer diameter of the insulated power leads 2. The lead-in openings26 accommodate the connector clips 15 and the adjacent ends of theterminal pins 8 and the insulated power leads 2. In particular, the endsof power leads 2 are inserted into the lead-in openings 26 with aportion of the insulating cover 14 Within the lead-in openings.

A sealant 2'7 completely fills all of the voids within the terminalcavity in the sheath 4 adjacent the open end of the sheath as well asall of the openings in the plug 22. The sealant is any suitableplastic-like material Which sets to .a relatively hardened state andwhich will bond to the adjoining surfaces to hermetically close the openend of the sheath 4. The sealant 27 fills the annular space or void 25between the inner end of the plug 22 and the sheath 4 to insure a firmand positive locking of the plug 21 within the opening and establishanexcellent seal between the adjoining surface of plug 22 and sheath 4.

The sealant 25 is preferably a thermo-setting plastic such as anepoxyresin which can be inserted as a liquid with hardening and curing agentsto flow into the sheath 4 and plug 22. Epoxy resins and the like alsobond to the adjoining surfaces upon setting to establish a positivesealing of the lead-in opening.

Referring particularly to FIG. 3, the plug 22 includes a filling openingor passage 28 extending axially through the plug 22 parallel to andspaced from the lead-in openings 26. An epoxy resin sealant 27 or othersuitable material is inserted through passage 28 to completely fill thecavity Within the outer end of the sheath 4 including the void betweenthe inner end of the plug 22 and the sheath 4. The air exhaustsoutwardly through the lead-in openings 26. The sealant 2-7 flowsoutwardly through the lead-in openings 26 to completely encase theterminal pins 8, the connector clips 16 and the adjacent ends of theleads 2. Upon curing, the sealant 27 hermetically closes the lead-inopening to positively prevent contamination of the refractory material 9or leakage of electricity from the heating unit into'the immersingliquid, not shown. The sealant 27 also bonds to the adjacent surfaces tophysically support the plug 22 as well as the physical connection of thecable 2 to the terminal pins 8.

Referring particularly to FIG. 4, the illustrated embodiment of theinvention is initially assembled in the following manner.

Plug 22 is assembledwith the leads 2 projecting outwardly through theaxial lead-in openings 26. The terminal pins {land the stripped ends 15of leads 2 are crimped and, if desired, soft soldered to the connectorclip 16, as previously described. The plug 22 is then moved down Wardlyalong the leads 2 and into the open end of the sheath 4 with theintermediate radial flange 23 seated against the end fin ill. Thecooperating tapered portion 2 3 of plug 22 and the taper in the outerend of sheath 4 facilitate the assembly of the plug 22 with the sheath4. The sealant 27 is then inserted through the filling passage 28 untilthe cavity within the sheath 4 is filled and the sealant fiows outwardlythrough the axial lead-in openings at to completely encase theinterconnection of the cable 2 to the terminal pins 8. The sealant isthen set to establish the hermetic enclosure and to support the plug 22.

Although illustrated in connection with a U-shaped heating element, theterminal connection of the present invention is equally applicable to astraight-through construction wherein the lead-in connections are madeat opposite ends of the unit, to a conventional cartridge type heater orto any other heating unit having a lead-in opening or openings to behermetically sealed.

The present invention. provides a positive and excellent hermeticclosure at the lead-in opening in an economical and simple mannerWithout the necessity of unsightly sealmg accessories.

Various modes of carrying out the invention are contemplated as withinthe scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In an electrical heating assembly having a heating element havingterminal pins connected to power leads, a housing having a lead-inopening and enclosing the heating elements with the terminal pinsprojecting outwardly through the opening, an electrically insulating andheat conducting medium filling the housing about the element anddefining a terminal cavity adjacent the opening, a plug member mountedwithin the opening with at least a portion of the surface of the plug indirect engagement with an interior portion of the housing andterminating in spaced relation to the medium, said plug having axiallead openings, connectors disposed within said axial lead openings andjoining the power leads and the terminal pins within said axial leadopenings, said plug having an assembly opening spaced from said leadopenings and extending through the plug from an exterior portion to theterminal cavity with the plug mounted within the lead-in opening, and athermo setting plastic material filling the terminal cavity and the leadopenings and the assembly opening in the plug to hermetically seal thelead-in opening of the housing and bonded to adjacent surfaces to lockthe plug within the opening and to mechanically support the terminalpins and power leads to the connector.

2. In an electrical heating assembly including a heating element withterminal pins connected to power leads, a tubular housing having atleast one open end and enclosing the heating elements with the terminalpins projecting through the opening, an insulating medium filling thehousing about the element and defining a terminal cavity adjacent theopen end, a tubular plug member mounted within the opening andterminating in spaced relation to the insulating medium, said plughaving axial lead openings accommodating the power leads and theterminal pins, connectors disposed within the axial openings in saidplug and having end clamps secured to adjacent end portions of the powerleads and the pins and having an intermediate soldered clamp joining thepower leads and the terminal pins, said plug member including an axialassembly opening extending 'therethrough, and a thermo setting plasticmaterial filling the terminal cavity and the lead openings and theassembly opening in the plug to hermetically seal the end of thehousing.

3. A terminal connection for a housed heating element having wire-liketerminal means passing outwardly through an open end of a tubularhousing for connection to insulated power supply lines, which comprisesconnecting means joining the power supply lines to the terminal means, atubular closure plug mounted in the open end of the housing and havingan outer radial flange seated on the end of the housing to locate thehousing, said plug having individual axial lead openings within whichthe connected terminal means and the supply line are located, said axiallead openings being larger than the incoming power supply lines tofreely receive the insulated lines, the outer surface of the end of theplug within the housing being tapered to establish an annular spacetherebetween, said plug member including an axial assembly openingextending therethrough, and a potting compound filling the open-end ofthe housing and the axial lead openings and the axial assembly openingof the closure plug to hermetically seal the lead-in opening and lockthe plug to the housing.

4. In an electrical heating assembly having a heating element withterminal pins connected to power leads, a housing having an open end andenclosing the heating elements with the terminal pins projecting throughthe open end, heat dissipating fins secured to the outer circumferenceof the housing and having an end fin extending perpendicular to the axisof the housing, said end fin constituting a nameplate to carryinformation relating to the heating assembly, an insulating mediumfilling the housing about the element and defining a terminal cavityadjacent the opening, a tubular plug member mounted within the openingand terminating in spaced relation to the insulating medium and havingan intermediate flange seated on the end fin to locate the plug, saidplug having axial power lead openings individually accommodating thepower leads and the terminal pins, a third axial opening extend ing inspaced parallel relation to said power lead openings, connectors joiningthe connected power leads and the terminal pins within the power leadopenings, the outer surface of the plug within the housing being taperedinwardly to define an annular space therebetween, the outer portion ofthe inner surface of the housing adjacent the plug being correspondinglytapered, and a thermo setting material filling the terminal cavity andthe axial openings in the plug to hermetically seal the end of thehousing.

5. In a method of sealing a terminal connection of a housed heatingelement having wire-like terminal means extended through a lead-inopening in the housing and connected to power supply lines, assembling aclosure plug having a filling opening and lead openings with theterminal ends of the supply lines so that the supply lines extendthrough said lead openings, connecting the supply lines to the terminalmeans, moving the closure plug along the supply lines and into thelead-in opening with the connection of the supply lines and terminalmeans being located within the lead openings, thereafter filling theplug and housing including the lead openings and the filling openingthrough the filling opening with a curable thermosetting plastic andcuring said thermosetting plastic to hermetically seal the lead-inopening.

6, In a method of sealing a terminal connection of a housed heatingelement having wire-like terminal means extended through a lead-inopening in the housing and connected to power supply lines, assembling aclosure plug having lead-in openings with the terminal ends of thesupply lines and having a filling opening generally parallel to thelead-in openings, connecting the supply lines to the terminal means,moving the closure plug along the supply lines and into the lead-inopening, and introducing a potting compound into the housing adjacentthe plug through the filling opening to completely fill the plug andhousing adjacent the opening with the potting compound and hermeticallyseal the lead-in opening.

7. A terminal connection for a housed heating element having terminalmeans extended through a lead-in opening in the housing for connectionto insulated power supply lines, which comprises connecting meansjoining the power supply lines to the terminal means, a closure plugmounted in said lead-in opening and having at least one longitudinallead opening within which the connected terminal means and the supplylines are located, said longitudinal lead opening being larger than theincoming power supply lines to freely receive the insulated lines, saidclo sure plug including a longitudinal potting opening spaced from saidlead opening, and a potting medium filling the housing adjacent thelead-in opening and the longitudinal openings of the closure plug andbonded to the adjacent surfaces to hermetically seal the lead-in openingand lock the plug within the opening.

References Cited in the file of this patent UNITED STATES PATENTS1,115,447 Liversidge Oct. 27, 1914 2,460,795 Warrick Feb. 1, 19492,508,512 Grinde May 23, 1950 2,892,989 Shroyer June 30, 1959 2,898,570Patrichi Aug. 4, 1959 2,911,683 Palermo et al Nov. 10, 1959 2,941,024Lamphier June 14, 1960 FOREIGN PATENTS 478,161 Great Britain Jan. 13,1938 1,149,844 France July 22, 1957

1. IN AN ELECTRICAL HEATING ASSEMBLY HAVING A HEATING ELEMENT HAVINGTERMINAL PINS CONNECTED TO POWER LEADS, A HOUSING HAVING A LEAD-INOPENING AND ENCLOSING THE HEATING ELEMENTS WITH THE TERMINAL PINSPROJECTING OUTWARDLY THROUGH THE OPENING, AN ELECTRICALLY INSULATING ANDHEAT CONDUCTING MEDIUM FILLING THE HOUSING ABOUT THE ELEMENT ANDDEFINING A TERMINAL CAVITY ADJACENT THE OPENING, A PLUG MEMBER MOUNTEDWITHIN THE OPENING WITH AT LEAST A PORTION OF THE SURFACE OF THE PLUG INDIRECT ENGAGEMENT WITH AN INTERIOR PORTION OF THE HOUSING ANDTERMINATING IN SPACED RELATION TO THE MEDIUM, SAID PLUG HAVING AXIALLEAD OPENINGS, CONNECTORS DISPOSED WITHIN SAID AXIAL LEAD OPENINGS ANDJOINING THE POWER LEADS AND THE TERMINAL PINS WITHIN SAID AXIAL LEADOPENINGS, SAID PLUG HAVING AN ASSEMBLY OPENING SPACED FROM SAID LEADOPENINGS AND EXTENDING THROUGH THE PLUG FROM AN EXTERIOR PORTION TO THETERMINAL CAVITY WITH THE PLUG MOUNTED WITHIN THE LEAD-IN OPENING, AND ATHERMO SETTING PLASTIC MATERIAL FILLING THE TERMINAL CAVITY AND THE LEADOPENINGS AND THE ASSEMBLY OPENING IN THE PLUG TO HERMETICALLY SEAL THELEAD-IN OPENING OF THE HOUSING AND BONDED TO ADJACENT SURFACES TO LOCKTHE PLUG WITHIN THE OPENING AND TO MECHANICALLY SUPPORT THE TERMINALPINS AND POWER LEADS TO THE CONNECTOR.